Did NASA Waive Safety?

Long before the shuttle Columbia was destroyed on re-entry last month, NASA scientists had considered literally hundreds of problems that might threaten the craft's safety--and decided to launch it anyway. Columbia had accumulated a thick sheaf of what in the rocket business are called safety waivers--problems that NASA had noted but decided posed too small a risk to bother with. "That's a pretty deep stack; it really is," a member of the Columbia Accident Investigation Board told TIME. "A lot of these [waivers] are legitimate--every launch is going to have them--but others are things you've learned to live with." The board...